1. Field of the Invention
The present invention relates to an electro-hydraulic variable valve lift apparatus and, more particularly, to an electro-hydraulic variable valve lift apparatus adaptive to have a simplified oil circuit to reduce oil flow path resistance.
2. Description of Related Art
An internal combustion engine takes in fuel and air to a combustion chamber and burns the same to generate power. In case of sucking air, an intake valve is operated by driving a cam shaft, and while the intake valve is open, air is sucked into the combustion chamber. Also, an exhaust valve is operated by driving the cam shaft, and while the exhaust valve is open, air is expelled from the combustion chamber.
However, an optimal operation of the intake valve and the exhaust valve varies according to a rotation speed of an engine. Namely, an appropriate lift or valve opening/closing time varies according to a rotation speed of an engine. Thus, in order to implement an appropriate valve operation according to a rotation speed of an engine, a plurality of cams for driving valves are designed, or a variable valve lift (VVL) apparatus in which a valve is operated at a different lift according to an engine RPM, a variable valve timing (VVT), an electro-hydro valve lift (EHV), and the like, have been searched.
In case of a generally used EHV apparatus, an oil circuit for an operation thereof is complicated and resistance of oil that passes through the complicated oil circuit is problematic.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.